1. Field of the Invention
This invention relates to a vibratory pile driver and particularly to a pile driver including at least one hydraulic gear motor, counter-rotating, semicircular weights, and means for driving the weights for transmitting vibratory forces to a pile or similar structure in a substantially linear direction.
2. Brief Description of the Prior Art
Conventional vibratory pile drivers include electric or hydraulic motor driven, counter-rotating, semicircular weights which are geared together to provide force components unidirectionally, that is only in a linear direction. Representative pile drivers are manufactured and/or sold by a number of United States and non-U.S. companies, including the assignee of the present invention.
Such pile drivers have capacities ranging from 30-200 tons centrifugal force and operate on the principle of using rotating eccentrics, usually semicircular weights, to cause vibration. The centrifugal force of the weights oppose each other, thus cancelling out any horizontal vibration component, and adding vertically resulting in only substantially linear vibration. In substantially all cases, the motor, which in the case of a hydraulic motor, is driven from a remote location, drives a shaft with the weights geared together. It is apparent that as the size of the gears increases, the pitch line velocity becomes so great that it is not practical to use gears.
Hence, belts or chains have been used in some pile drivers to connect a motor to one or more shafts upon which the weights are mounted, as shown for example in U.S. Pat. Nos. 3,280,924; 3,396,805; and 3,828,864.
However, in none of the foregoing patents, nor in any prior art of which I am aware, has a hydraulic gear motor been provided with two shafts driven counter-rotationally and been used to drive the weights in a vibratory pile driver in opposite directions, while simultaneously synchronizing the weight rotation, whether or not belts or chains have been provided. Moreover, none of the art discloses or suggests that additional conventional single-shaft hydraulic motors can be used to supplement the power transmitted to the weights from an electric or hydraulic motor.
In order to provide maximum vibratory force in a pile driver, one object of the present invention is to eliminate relatively large gears. Another object is to reduce the number of gears and shafts required to transmit maximum vibratory forces to piles or other structures to be driven or extracted. A further object of the invention is to maintain synchronization of the weights in order to concentrate forces in the vertical direction only. A further object of the invention is to permit the use of larger diameter weights without the use of large diameter gears and high pitch line velocities. A still further object is to limit the width of the driver so that it can be used to drive piles, e.g. sheets of about 14"-18" wide, between adjacent piles.